This invention relates generally to aerial spray marking of earth surfaces and more particularly to an aerial spray marking system that produces highly forceful shot of marking substance capable of penetrating dense foliage.
There are many situations in which a need arises to mark off or delineate large land areas. For instance, it is common in the forestry industry to first mark large blocks of forested land prior to sending crews in for harvesting, commercial thinning or pre-commercial thinning, thereby clearly indicating to the crews the boundaries of the block or blocks to be cut. Other industries where the need to mark off large land areas arises include agriculture, civil engineering and telecommunications. Land marking is also applicable for many military purposes.
Normal methods for marking forestry boundaries for commercial and pre-commercial thinning blocks and mature growth harvest areas are walking the boundaries of the areas on foot and placing a flag or other marker every few feet. This process is labor intensive and time consuming in that it takes a large crew of workers a long time to mark off even a modestly sized block. The time requirements are exacerbated by the fact that such areas are typically difficult to traverse because of dense growth. Even on non-forested areas, the large areas generally required to be marked limit the efficiency of manual marking.
Because of the large time requirement, marking is ordinarily started well in advanced of the planned cut. This means that the markers are often missing or disturbed by the time the cutting crew arrives at the site. Thus, conventional marking processes are not always sustainable long enough to achieve the desired objective of indicating the boundaries to be cut.
Accordingly, there is a need for a method and apparatus that is able to easily and quickly mark ground surfaces, regardless of the nature of the terrain. Such marking should also be sustainable over long periods of time.
The above-mentioned need is met by the present invention, which provides a system and method for aerial spraying, particularly spray marking, of ground surfaces. The system includes a storage tank for holding a substance, means for pressurizing the storage tank, a spray nozzle assembly, and a feed line for delivering pressurized substance from the storage tank to the spray nozzle assembly. In one preferred embodiment, the means for pressurizing the storage tank includes a cylinder of compressed gas that is connected to the storage tank by a gas carrying system comprising a pressure regulator, a high pressure line connecting the cylinder to the pressure regulator, and a first regulated gas line connecting the pressure regulator to the storage tank. The spray nozzle assembly includes a first valve connected to the feed line, a spray nozzle connected to the first valve, and a second valve arranged to open and close the first valve. A second regulated gas line connects the pressure regulator to the spray nozzle assembly such the pressurized gas will open or close the first valve depending on the state of the second valve. The substance will be discharged from the spray nozzle whenever the first valve is open.
A controller is provided for automatically controlling the opening and closing of the first valve in accordance with user selected settings. The system can include a pressure transducer for sensing the pressure of gas output from the pressure regulator. The controller can thus close a shut off valve disposed in the feed line in response to the sensed pressure falling below a predetermined level. The storage tank, cylinder and spray nozzle assembly are all mounted on a frame, which can be supported from an aircraft. Thus, in operation, the system is suspended or otherwise mounted below an aircraft and flown over the target site. At which point, the spray nozzle assembly is selectively activated so as to spray pressurized substance onto the ground surfaces. For aerial spray marking applications, the substance would be a marking substance such as paints, dyes and the like.